Bacterial contamination of foods is known to be responsible for spoilage and for the transmission of food borne illness. This problem is particularly acute in ready to eat meats and dairy products which are not normally reheated by consumers prior to ingestion. As a result, a great deal of effort has been expended in attempts to identify low cost natural products that can be safely added to foods for the purpose of inhibiting bacterial growth.
Bacteriocins are antimicrobial peptides that are produced by bacteria and which have a bactericidal or bacteristatic action against closely related species. The most extensively characterized bacteriocin is nisin which is produced by a lactic acid type bacteria and which may be used to prevent the growth of Gram-positive bacteria in a variety of different food products (see e.g., U.S. Pat. No. 2,744,827; U.S. Pat. No. 4,584,199; U.S. Pat. No. 4,597,972 and U.S. Pat. No. 5,527,505). Bacterial species used for the isolation of bacteriocins have included propionic acid bacteria (U.S. Pat. Nos. 5,096,718; 5,260,061), Streptococcus or Pediococcus bacteria (U.S. Pat. Nos. 5,573,797; 5,593,800; 5,573,801), and Micrococcus varians (U.S. Pat. No. 6,150,139).
Although several bacteriocins have been identified, those that are effective against Gram-negative bacteria are relatively rare. Thus, the identification of new bacteriocin compounds of this type is of importance in extending our ability to protect foods and other compositions. Ideally, these peptides should be safe, have a broad spectrum of activity and be stable over a wide range of pHs and temperatures.